Железо в неживой и живой природе

Abstract

The paper considers crystal structure and chemical properties of iron, its oxidation numbers and participation of iron in redox processes in animate and inanimate nature. Depending on temperature and pressure, iron can have five crystal structures: a, b, g, d and e. Sketches of unit crystal cells are drawn. Interstices that may be occupied by impurity atoms are shown. Iron may have oxidation numbers from zero (pure iron) to +8. The most important are oxidation numbers of 0, +2 and +3. Iron oxide +2 (FeO) has black colour, while iron oxide +3 (Fe2O3) is bright red. Iron is the key participant in the process of oxygen transfer in steelmaking processes. The transfer processes consists of acquisition of oxygen by iron at the cost of its oxidation to FeO (Fe+2) and Fe2O3 (Fe+3), oxygen being transferred to the metal melt [O]. Redox processes and oxygen transfer processes are bound with the change of iron oxidation number. A doubt is expressed on oxygen attachment to hemoglobin in molecular form,, and a writing of reactions involving hemoglobin in the blood based on redox reactions is proposed. Reactions of oxygen transfer by the blood are proposed. In the lungs, where partial oxygen pressure is high, a part of Fe+2 of the hemoglobin gives electrons and oxidates to Fe+3, which results in the change of the blood colour: (Hb·4Fe+2) + O2 ↔ (Hb·4Fe+3·2O–2). In the capillars, Fe+3 attaches electrons, gives oxygen participating in oxidation, and reduces to Fe+2: (Hb·4Fe+3·2O–2) + Cсреды = (Hb·4Fe+2) + CO2. In this writing of reactions there is no place for molecular oxygen. In accordance with the present scheme, redox reactions in the lungs and capillars occur at a high rate with participation and transfer of electrons.